diff --git a/drivers/c64_cps.s b/drivers/c64_cps.s
index dbecd6f..1ad88f3 100644
--- a/drivers/c64_cps.s
+++ b/drivers/c64_cps.s
@@ -2,11 +2,11 @@
 ; CC65's C64 runtime library doesn't provide this function
 ; this file provides a version in order that clk_timer.s works without 'ifdefs'
 
-.export __clocks_per_sec
+.export ___clocks_per_sec
 
 .code
 
-__clocks_per_sec:
+___clocks_per_sec:
   lda #60
   rts